It's like this:
Superfree is food to fill up on, very healthy, that will not encourage you to put weight on. It's basically fruit and veg, minus avocados and starchy veg, like potatoes
Speed foods are foods that actively encourage weight loss, due to some properties in the food. Superspeed are the top end of this. For example, some fruit/veg, like strawberries, take more calories to burn up than they contain. So you end up in negative calories! Other foods have high fibre content, that aids weight loss by assisting your gastrointestinal tract and by making it more difficult for your body to absorb calories from food. An example would be baked beans. Still others have low fat but high protein content, proven to fill you up for longer and thus reduce amount of food consumed. An example would be chicken.
Some foods fall into both categories, I.e strawberries, which is fab! You can eat loads of them AND they assist weight loss! Cool! You can't just scoff down shed loads of speed foods that aren't also superfree though. Although a portion or so of chicken will aid weight loss, it still has a much higher calorie content than berries, and if you chow it down all day, you're not going to lose any weight.
Hope that helps and doesn't make me sound too nerdy!